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AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency
Hein ten Horn wrote:
quote We hear the average of two frequencies if both frequencies are indistinguishably close, say with a difference of some few hertz. For example, the combination of a 220 Hz signal and a 224 Hz signal with the same amplitude will be perceived as a 4 Hz beat of a 222 Hz tone. unquote (..) From the example: there's no 222 Hz tone in the air. That one I'd like to take back. Obviously the superposition didn't cross my mind. The matter is actually vibrating at the frequency of 222 Hz. Not at 220 Hz or 224 Hz. gr, Hein |
AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency
Ron Baker, Pluralitas! wrote:
David L. Wilson wrote: Hein ten Horn wrote: ... So take another example: 25000 Hz and 25006 Hz. Again, constructive and destructive interference produce 6 Hz amplitude variations in the air. But, as we can't hear ultrasonic frequencies, we will not produce a 25003 Hz perception in our brain. So there's nothing to hear, no tone and consequently, no beat. If one looks at an oscilloscope of the audio converted to voltage, one still can see the 6Hz variations on the 25003 Hz and still refers to those as tone and beat. These exist in mathematically formulation of the resulting waveforms Right. not just as something in the brain. In this particular example nothing is heard because 25003 Hz is an ultrasonic frequency. What is the mathematical formulation? sin(2 * pi * f_1 * t) + sin(2 * pi * f_2 * t) or 2 * cos( pi * (f_1 - f_2) * t ) * sin( pi * (f_1 + f_2) * t ) So every cubic micrometre of the air (or another medium) is vibrating in accordance with 2 * cos( 2 * pi * 3 * t ) * sin(2 * pi * 25003 * t ), thus having a beat frequency of 2*3 = 6 Hz and a vibration frequency of 25003 Hz (let alone phase differences of neighbouring vibrating elements). gr, Hein |
AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency
On Jul 1, 11:11 am, Jeff Liebermann wrote:
John Smith I hath wroth: RHF wrote: ... Because "Radium" Touched Them With A Thirst For Knowledge And A Quest For Answers. ... I don't know, according to any instructor I have ever had respect for: "There are NO stupid questions, only stupid people who are afraid to ask questions." I beg to differ. My favorite mentor/instructor/employer had a different philosophy regarding questions and answers. His line was something like "If you don't understand the problem, no solution is possible". His method was to concentrate on understanding the problem, refining the corresponding questions, and only then concentrating on finding the answer. I would spend much more time thinking about "what problem am I trying to solve" instead of blundering prematurely toward some potentially irrelevant solution. My problem with the original question is that it fails to associate itself with anything recognizable as a real problem to solve or a theory to expound. In my never humble opinion, if there was a question under all that rubbish, it was quite well hidden and severely muddled. He also introduced a substantial number of "facts" that varied from irrelevant to incoherent to just plain wrong. The problem for us in not in finding the answer, but in decoding the question. There may not be any stupid questions, but there seem to be a substantial number of marginal people asking questions. I answer some techy questions in alt.internet.wireless. What I see, all too often, are people that seem to think that no effort on their part is necessary to obtain an answer. They exert no effort to read the FAQ, no effort to supply what problem they are trying to solve, and no effort to supply what they have to work with. In this case, Mr Radium has either exerted no effort to compose his question in a form that can be answered, or if there was such an effort, it has failed miserably. He couldn't even find a suitable collection of newsgroups for his question. There may not be any stupid questions, but there certainly are questions not worth the time attempting to answer. If Mr Radium had left the question at the subject line: "AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency" the question would have been easy to answer, as several people have done. However, those that answered and I all did the same thing. We extracted from the word salad question what we thought was something resembling a coherent question, and ignored the rest of the rubbish. In other words, we did the necessary simplification and problem reduction, and discarded the bulk of the incoherent residue. There may not be any stupid questions, but if you bury it under a sufficient number of words, it may closely resemble a stupid question. Depends ... I guess. JS Well, let's see: http://groups.google.com/groups?as_q=%22guess%28tm%29%22&as_uauthors=... 533 guesses, out of about 16,000 postings, which I guess(tm) isn't all that bad. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 thankyou, for the wonderfully varied responses. here's my question? as one who simply asks the questions! can fm waves ( any kind) PIGGY BACK ON AM WAVES? THE IMPLICATIONS ARE FAR REACHING!!!!!!!!! REMEBER AS OUR GREAT ANCESTORS SO ELOCENTLY PUT IT (PARAPHRASED) WHEN CONSIDERING THE LIGHT BULB " I FOUND 2000 NEW WAYS OF THINKING" BUT THIS GREAT MAN DIDNT FINNISH UNTIL THE GOAL WAS REACHED ADMIRABLE QUALITIES. personally speaking, I have no formal or imformal education that can match the depths of this scientific quorum. I do have a vision I hope to find new ways every day of connecting so i can get to the beaches where the waves and the people think outside the box of normal surfing and envision a whole new world metaphoricaly speaking. Im a beach boys fan!!!!!!!! |
AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-lowcarrier frequency
Hein ten Horn wrote: Hein ten Horn wrote: quote We hear the average of two frequencies if both frequencies are indistinguishably close, say with a difference of some few hertz. For example, the combination of a 220 Hz signal and a 224 Hz signal with the same amplitude will be perceived as a 4 Hz beat of a 222 Hz tone. unquote (..) From the example: there's no 222 Hz tone in the air. That one I'd like to take back. Obviously the superposition didn't cross my mind. The matter is actually vibrating at the frequency of 222 Hz. Not at 220 Hz or 224 Hz. gr, Hein You were correct before. It might be correct to say that matter is vibrating at an average, or effective frequency of 222 Hz. But the only sine waves present in the air are vibrating at 220 Hz and 224 Hz. Obviously. It's a very simple matter to verify this by experiment. You really ought to perform it (as I just did) before posting further on the subject. jk |
AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency
craigm wrote:
Jim Kelley wrote: David L. Wilson wrote: Jim Kelley wrote: At a particular instant in time the period does in fact equal the average of the two. But this is true only for an instant every 1/(a-b) seconds. How do you come up with anything but a period of of the average of the two for the enveloped waveform? The error here is in assuming that the sin and cos terms in the equivalent expression are representative of individual waves. They are not. The resultant wave can only be accurately described as the sum of the constituent waves sin(a) and sin(b), or as the function 2sin(.5(a+b))cos(.5(a-b)). That function, plotted against time appears exactly as I have described. I have simply reported what is readily observable. I would submit you plotted it wrong and/or misinterpreted the results. Jim, if you'd like me to send you an Excel sheet about this, please let me know. gr, Hein I've sent this post already once. For some strange reason it didn't come up in rec.radio.shortwave (craigm?). I only read rec.radio.shortwave these days. (repost to: sci.electronics.basics, rec.radio.shortwave, rec.radio.amateur.antenna, alt.cellular.cingular, alt.internet.wireless) |
AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency
"Rich Grise" wrote in message ... On Wed, 11 Jul 2007 22:52:17 -0700, Jeff Liebermann wrote: "NotMe" hath wroth: (Please learn to trim quotations) Actually the human ear can detect a beat note down to a few cycles. If you are talking about the beat between two close audio frequencies then one can easily hear a beat way below 1 Hz. No, you cannot. Figure on 20Hz to 20KHz for human hearing: http://hypertextbook.com/facts/2003/ChrisDAmbrose.shtml What happens when you zero beat something is that your brain is filling in the missing frequencies. As you tune across the frequency, and the beat note goes down in frequency, most people overshoot to the other side, and then compensate by splitting the different. If you are talking about beat frequency heard when tuning to a carrier with a radio with a BFO or in SSB mode then one can't hear any beat below 50 Hz or so. The audio section of the receiver blocks anything below about 50 Hz. No, you've got it all wrong. The beat note happens because, when the signals are close to 180 degrees out of phase, they cancel out such that there is, in fact, no sound. This is what your ear detects. Now, if you're zero-beating, say, 400 Hz against 401 Hz, I don't know if the 801 Hz component is audible or if it's even really there, but mathematically, it kinda has to, doesn't it? Are you talking radios or guitars? With a guitar you might beat 400 Hz against 401 Hz. With a radio you'd more likely beat 455 kHz against 455.001 kHz. Thanks, Rich |
AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency
"Ron Baker, Pluralitas!" wrote in message ... | | "Rich Grise" wrote in message | ... | On Wed, 11 Jul 2007 22:52:17 -0700, Jeff Liebermann wrote: | | "NotMe" hath wroth: | | (Please learn to trim quotations) | | Actually the human ear can detect a beat note down to a few cycles. | | If you are talking about the beat between two close | audio frequencies then one can easily hear a beat way | below 1 Hz. Based on studies done at Tulane Department of Neurology (mid 60's) the detection is not in the ear but in the brain. The process can be taught and refined though bio-feedback. |
AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency
"Hein ten Horn" wrote in message ... Ron Baker, Pluralitas! wrote: David L. Wilson wrote: Hein ten Horn wrote: ... So take another example: 25000 Hz and 25006 Hz. Again, constructive and destructive interference produce 6 Hz amplitude variations in the air. But, as we can't hear ultrasonic frequencies, we will not produce a 25003 Hz perception in our brain. So there's nothing to hear, no tone and consequently, no beat. If one looks at an oscilloscope of the audio converted to voltage, one still can see the 6Hz variations on the 25003 Hz and still refers to those as tone and beat. These exist in mathematically formulation of the resulting waveforms Right. not just as something in the brain. In this particular example nothing is heard because 25003 Hz is an ultrasonic frequency. What is the mathematical formulation? sin(2 * pi * f_1 * t) + sin(2 * pi * f_2 * t) or 2 * cos( pi * (f_1 - f_2) * t ) * sin( pi * (f_1 + f_2) * t ) So every cubic micrometre of the air (or another medium) is vibrating in accordance with 2 * cos( 2 * pi * 3 * t ) * sin(2 * pi * 25003 * t ), thus having a beat frequency of 2*3 = 6 Hz How do you arrive at a "beat"? Hint: Any such assessment is nonlinear. (And kudos to you that you can do the math.) Simplifying the math: x = cos(a) * cos(b) = 0.5 * (cos[a+b] + cos[a-b]) (Where a = 2 * pi * f_1 * t and b = same but f_2.) All three of the above are equivalent. There is no difference. You get x if you add two sine waves or if you multiply two (different) sine waves. So which is it really? Hint: If all you have is x then you can't tell how it was generated. What you do with it afterwards can make a difference. and a vibration frequency of 25003 Hz (let alone phase differences of neighbouring vibrating elements). gr, Hein |
AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency
"Ron Baker, Pluralitas!" wrote in message ... | | "Rich Grise" wrote in message | ... | On Wed, 11 Jul 2007 22:52:17 -0700, Jeff Liebermann wrote: | | "NotMe" hath wroth: | | (Please learn to trim quotations) | | Actually the human ear can detect a beat note down to a few cycles. | | If you are talking about the beat between two close | audio frequencies then one can easily hear a beat way | below 1 Hz. But what you hear below ~20 Hz is not the beat note, but changes in sound pressure (volume) as the mixing product goes in and out of phase. This actually becomes easier to hear as you near zero beat. |
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